Conventional Mobile Ad hoc Networks (MANETs) are executed by an Internet Protocol (IP) and face many of the same Quality of Service (QoS) challenges that traditional hardwired networks encounter (FIG. 1). MANETs may have additional constraints, such as limited bandwidth, dynamic topologies, and reduced processing capability. Therefore, an increased probability of congestion and “jitter” may also be present.
In any network, performance and reliability are significantly impacted by the network's topology. In traditional wired networks, the topology is static, allowing for an engineered network design to meet system requirements. However, in the case of mobile ad hoc networks (MANETs), the network topology is not only dynamic, but often unstable and unpredictable. Arbitrary deployments, node mobility, variable link quality, and physical vulnerabilities conspire to undermine engineered network design and resource over-provisioning. For a network to maintain its capability and robustness, the network must adapt its operation based on accurate knowledge of system state.
Adaptive topology management schemes aim to mitigate the inherent volatility of a MANET network topology by dynamically tuning communication resources based on a combination of local and global information. To improve topological stability, a node may configure communication resource parameters in such a way as to preserve connectivity with an existing neighbor, or inhibit connectivity with a potential new neighbor.
Alternatively, a network may alter current topology to better meet system requirements. Neighbors may be selectively dropped to reduce local interference and traffic bottlenecks. Neighboring connectivity may be extended to prevent network partitioning or provide alternate routes for fault-tolerance and traffic load balancing.
The effectiveness of adaptive topology management is limited by the configurability of a node's communication resources. At the coarsest level, a node can alter its local connectivity simply by enabling or disabling its communication interfaces. Transmission power adjustments offer a finer degree of control, allowing a node to selectively establish connectivity with nodes within a certain range. More advanced antenna control mechanisms (at the transmitter and/or receiver ends) may allow local connectivity to be constrained within a more customizable region, according to a configurable antenna beam pattern.
With regard to protocol architecture, adaptive topology management depends on physical layer resources (i.e., transceivers, antennas, radio controllers, etc.) being controlled based on network state and performance metrics maintained by higher layers in the protocol stack. This is incompatible with standard layered network architectures, where protocol layers operate with limited, or no, cross-layer interaction. A more flexible cross-layer interface to effectively convey information and control directives between layers is desirable.